Optical and mechanical properties of transparent SrTiO3 thin films deposited by ECR ion beam sputter deposition

Authors

  • Gasidit Panomsuwan,

    Corresponding author
    1. Department of Materials, Physics, and Energy Engineering, Graduate School of Engineering, Nagoya University, Furo-cho, Chikusa-ku, 464-8603 Nagoya, Japan
    • Phone: +81 52 789 5274, Fax: +81 52 789 4998
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  • Osamu Takai,

    1. Department of Materials, Physics, and Energy Engineering, Graduate School of Engineering, Nagoya University, Furo-cho, Chikusa-ku, 464-8603 Nagoya, Japan
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  • Nagahiro Saito

    1. Department of Materials, Physics, and Energy Engineering, Graduate School of Engineering, Nagoya University, Furo-cho, Chikusa-ku, 464-8603 Nagoya, Japan
    2. EcoTopia Science Institute, Nagoya University, Furo-cho, Chikusa-ku, 464-8603 Nagoya, Japan
    3. Green Mobility Collaborative Research, Nagoya University, Furo-cho, Chikusa-ku, 464-8603 Nagoya, Japan
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Abstract

SrTiO3 (STO) thin films have been deposited on glass substrates by electron cyclotron resonance (ECR) ion beam sputter deposition at different substrate temperatures (100–600 °C). The structural characteristics of the deposited films show a transition from amorphous phase to polycrystalline phase at 600 °C. The films exhibit good transparency with an interference pattern in the visible region and a very smooth surface without cracks. The refractive index of the films increases with an increase of the substrate temperature, and their dispersion was analyzed by a single-oscillator model. The extinction coefficient of the films in the visible region is of the order of 10−3–10−2. The estimated values of the direct and indirect bandgap energies for the polycrystalline STO film are 3.80 and 3.32 eV, respectively. Its density is almost identical to the bulk STO single crystal, which is relatively high in comparison with those prepared by other techniques. The mechanical stability of the films is also improved with an increase of substrate temperature. Young's modulus and hardness of the polycrystalline STO film are 194.1 ± 15.5 and 22.5 ± 2.0 GPa, respectively.

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